Add Settings > Gateway > Remote Gateway mode: when enabled, ClawX
attaches to an external OpenClaw Gateway (remote Linux host or SSH
port-forward) over ws(s):// instead of spawning a local process.

- ws-client accepts a url override; default stays ws://localhost
- startup orchestrator connectRemote branch skips all local process
  discovery/spawn/doctor-repair hooks
- stop() never sends shutdown to a remote Gateway; reconnects are
  transport-only so a dropped tunnel cannot silently drift the session
  to a locally spawned Gateway
- ACP child gets OPENCLAW_GATEWAY_URL + effective remote token
- Control UI opens the remote origin; channel activation skips forced
  restarts on external gateways; doctor refuses to run in remote mode
- gatewayRemote settings flow through store/contract/renderer with
  draft+save UI and en/zh/ja/ru i18n
- unit tests, settings-remote-gateway E2E spec, harness task spec
- harness specs parse frontmatter under CRLF checkouts (Windows
  core.autocrlf) so validate/run work locally